A group of computed tomography (CT) descriptors were derived for abdominal aortic aneurysms. Terminology was defined and applied to the interpretation of the CT image in 55 prospective cases. Correlation of geometric parameters of aneurysm and analysis of the relationship of internal aneurysm components such as lumen and thrombus was performed. Predictive growth patterns for aneurysm demonstrated a synchronous increase in the volume of thrombus within the aneurysm in those aneurysms measuring 5 to 7 cm. Aneurysms greater than 7 cm were associated with an expansion of the patent pulsatile lumen, with no appreciable increase in thrombus volume. The thrombus-lumen ratio effectively described the changing internal architecture of aneurysm associated with increase in size. Proper utilization of CT descriptors develops a language that interprets aneurysm stability and potential for rupture and may provide an improved basis for timely surgical planning.